Electronic structure of tris(8-hydroxyquinolato) aluminum at room temperature and during annealing

We have employed synchrotron radiation photoemission to investigate the electronic structure of tris(8-hydroxyquinolato) aluminum (Alq₃) at room temperature as well as at elevated temperatures. The dependence of the molecular state cross sections on the photon energy is demonstrated. Three chemical environments of carbon are resolved, accompanied with at least two shake-up satellite structures. Small loss structures are detected in other N $1s$, O $1s$, and Al $2p$ core-level spectra, but with various magnitudes. Annealing produces charge redistribution of the molecular states within Alq₃ itself. Alq₃ is stable at high temperature.